Did you draw a picture of the region you are integrating? If I'm drawing it correctly it doesn't look like you can do it as a single integral. You'll need to break it into pieces and think about using different origins for the polar coordinates for different pieces. Looks kind of nasty.

yes， i did, even ask my professor on how to doing it, but she only gave me the r=7+7cos(theta) but that doesn't make sense, i thought it's 14cos(theta), Dick, i completely loss, can anyone help me on this one

First of all there are three curves to worry about. The circle of radius 14, the circle of radius 7 and the line y=7. Which one corresponds to the polar equation r=7+7cos(theta)? What are the polar equations of the other two?